LTM-T
Modbus & Serial Output Transmitter
for
Thermocouple & RTD Temperature Exceptional linearity & accuracy at high update rates.
DIN Rail mounted, digitally
programmable.
Standard Features
Input for thermocouple types J, K, T, E, N, R, S.
Input for 100 ohm platinum RTDs
with DIN and ANSI curves.
2, 3 or 4-wire RTD connection
with lead resistance compensation.
Upscale or downscale open sensor
indication.
User selectable spans from entire
TC or RTD range down to 15.0°
Output update rate to 60/sec.
RS232 or RS485 serial communications,
half or full duplex, isolated.
Modbus RTU, Modbus ASCII
or Laurel ASCII protocol.
Dual solid state relays for alarm or control,
isolated.
0-10V, 4-20 mA or 0-20 mA analog output,
scalable, isolated.
Universal AC power, 95-240 Vac ±10%
Priced at only $235
(basic temperature transmitter)
Options:
Low voltage power,
10-48 Vdc or 12-30 Vac.
Description
The Laureate LTM-T serial
output temperature transmitter provides
a linearized, highly accurate, stable
and repeatable transmitter output for multiple thermocouple types and 100 Ohm platinum RTDs. The transmitter accepts the outputs of types J, K, T, E, N, R
or S thermocouples, plus
100 ohm platinum RTD’s with DIN alpha of 0.00385 or ANSI alpha of 0.003925. The
thermocouple or RTD type and temperature range, specified in °C or °F, are
user-selectable.
All ranges for all temperature sensor types
are digitally calibrated at the factory, with calibration data stored
in EEPROM on the signal conditioner board. This allows signal
conditioner boards and ranges to be changed in the field with no need for
recalibration. Cold junction compensation automatically
corrects for temperature variations at the thermocouple reference junction at the
transmitter.
Open sensor indication is standard and may be set up to indicate either upscale or
downscale. RTD excitation is provided by the transmitter. RTD connections can be of the 2-, 3-
or 4-wire type. For 3- and 4-wire connections, the transmitter automatically compensates for
lead resistance of the sensor.
Fast read rate at up to 50
or 60 conversions per second while integrating the signal over a
full power line cycle is provided by Concurrent Slope (Pat 5,262,780)
analog-to-digital conversion. High read
rate is ideal for peak or valley capture and for real-time computer interface and control.
LTM Series serial
output transmitters send data via an isolated serial port, which is user
configurable for RS232 or RS485 and full or half duplex operation. Three
protocols are user selectable: Modbus RTU, Modbus ASCII, or Laurel ASCII. Modbus operation
is fully compliant with Modbus Over Serial Line Specification V1.0 (2002).
The Laurel ASCII
protocol allows up to 31 Laureate devices to be addressed on the
same RS485 data line. It is simpler than the Modbus protocol and is
recommended when all devices are Laureates. It also allows use of
Laurel Datalogging Software.
Standard features of Model
LTM-T include:
Serial data output, isolated. User selectable RS232 or RS485, half or full duplex, Modbus or
Laurel ASCII protocol.
Dual solid state relays for control or alarm, isolated.
Rated 120 mA at 130 Vac or 170 Vdc.
Analog transmitter output, 16-bit, user scalable and isolated. User selectable 4-20 mA,
0-20 mA or 0-10V levels.
Universal AC power supply for 95-240 Vac ±10%.
Easy Transmitter programming is via
Laurel's Instrument Setup Software,
which runs on a PC under MS Windows. This software can be downloaded from this website at no charge. The required transmitter-to-PC interface cable is available from
Laurel (P/N CBL04).
Specifications
LTM-T Modbus & Serial I/O Transmitter
for Thermocouple & RTD Temperature
Thermocouple Input
TC Type
Range
Conformity
Error
J
-210°C to
+760°C
-347°F to +1400°F
0.09°C
0.16°F
K
-244°C to
+1372°C
-408°F to +2501°F
0.1°C
0.17°F
T
0°C to
+400°C
-257°C to 0°C
+32°F to 752°F
-430°F to +32°F
0.03°C
0.2°C
0.05°F
0.36°F
E
-240°C to
+1000°C
-400°F to +1830°F
0.18°C
0.32°F
N
-245°C to
+1300°C
-410°F to +2370°F
0.10°C
0.17°F
R
-45°C to
+1768°C
-49°F to +3214°F
0.17°C
0.31°F
S
-46°C to
+1768°C
-51°F to +3213°F
0.12°C
0.22°F
Applicable
to all thermocouple types
Calibration
Input resistance
Input current
Max lead resistance
Overall accuracy
Span tempco
Reference junction tempco
Span tempco
Over-voltage protection
NMR at 50/60 Hz
CMR, DC-60 Hz
CMV, DC-60 Hz
Open sensor indication
NIST
Monograph 125 (IPTS-68)
1 Gohm
100 pA
1 kohm max for rated accuracy
±0.01 of full scale ±2 counts
±0.003% of reading/ºC
±0.02 deg/deg
±0.003% of reading/ºC
125 Vac
80 dB plus selectable filter from 80 ms
to 9.6 s time constant
120 dB with 500 W imbalance
250 Vac from power and earth grounds
0 mA or > 20mA output, selectable
Pt 100 RTD Input
RTD Alpha
Range
Conformity
Error
DIN
.00385
-202°C to
+850°C
-331°F to +1562°F
0.03°C
0.05°F
ANSI
.003925
-202°C to
+631°C
-331°F to +1168°F
0.04°C
0.07°F
Applicable
to all RTD types
Calibration, DIN
Calibration ANSI
Configuration
Excitation current
Overall accuracy
Span tempco
Zero tempco
Sensor lead resistance
tempco per conductor
Over-voltage protection
Open sensor indication
IEC 751 (IPTS-68)
NIST Monograph 126
2, 3 or 4-wire connection
0.2 mA
±0.01 of full scale ±2 counts
±0.003% of reading/ºC
±0.03 deg/deg
2-wire, 10 mdeg/W/deg up to 10 W
3 & 4-wire, 10 mdeg/W/deg up to 100 W
125 Vac
0 mA or > 20mA output, selectable
Thermocouple & RTD
Serial Data Output
(standard)
Signal Types
Data Rates
Output Isolation
Serial Protocols
Modbus Modes
Modbus Compliance
Digital Addressing
RS232 or RS485 (half or full duplex)
300, 600, 1200, 2400, 4800, 9600, 19200 baud
250V rms working, 2.3 kV rms per 1 min test
Modbus RTU, Modbus ASCII, Laurel ASCII
RTU or ASCII
Modbus over Serial Line Specification V1.0 (2002)
247 Modbus addresses.
Up to 32 devices on an RS485 line w/o a repeater.
4-20 mA, 0-20 mA, 0-10 Vdc (jumper selectable)
10V ( 0-500 ohm load )
2 mA ( 5 kOhm load or higher)
16 bit DAC
±0.02% of output span plus conversion accuracy
250V rms working, 2.3 kV rms per 1 minute test
Dual Relay Output (standard)
Relay Type
Load rating
Two solid state relays, SPST, normally open,
Form A
120 mA at 130 Vac or 170 Vdc, 28 ohms in series
Power Input
Standard power
Low power option
Power frequency
Power Isolation
95-240 Vac ±10% or 90-300 Vdc (DC operation not UL approved)
10-48 Vdc or 12-30 Vac
DC or 47-63 Hz
250V rms working, 2.3 kV rms per 1 min test
Mechanical
Case Dimensions
Case Mounting
Electrical Connections
120 x 101 x 22.5 mm
35 mm rail per DIN EN 50022
Detachable screw-clamp plugs
Environmental
Operating Temp.
Storage Temp.
Relative Humidity
0°C to
70°C
-40°C to 85°C
95% at 40°C, non-condensing
Specifications LTM-T Modbus & Serial I/O
Transmitter
for Thermocouple & RTD Temperature
Laureate temperature
transmitters
allow 2, 3 or 4-wire RTD hookup to the J5 connector. The transmitter applies an excitation
current of 0.2 mA, which it monitors to make ratiometric corrections for excitation supply
variations.
In 2-wire hookup, the
transmitter
senses the voltage drop across the 100 ohm RTD and both lead wires. The effect of the lead
wires can be measured and subtracted by shorting out the RTD during
transmitter setup.
In 3- and 4-wire hookup, the
transmitter senses the voltage drop across the 100 ohm RTD and both lead wires as well as the
voltage drop across the RTD and one lead wire. This allows the transmitter to determine the effect of
one lead wire and mathematically subtract the effect of both lead wires.
Operation as a
Fast ON/OFF Controller
or Supervisory Monitor
With the optional dual solid state relay output
option, which has a typical response
time of only 17 ms, Laureate temperature meters
and transmitters can
serve as extremely fast and accurate ON/OFF controllers
for closed-loop temperature control.
They can also serve as
supervisory process monitors and provide alarms or shutoffs when processes exceed normal
limits.
Multiple setpoint operating modes are
individually selectable for each relay, as explained in the
dual-setpoint controller page. Relay duty cycles and chatter can be minimized with programmable hysteresis and
time delays. A band deviation operating mode can be
selected for each relay, where an alarm is generated whenever the reading is a selected
number of counts above or below the setpoint. With Modbus, relay operation
can be non-latching or latching, with reset provided by digital commands.
Ordering
Guide LTM-T Modbus & Serial I/O Transmitter
for Thermocouple & RTD Temperature Click
on the radio buttons to build a model number with pricing.
All ranges for all temperature sensor types
are digitally calibrated at the factory, with calibration data stored
in EEPROM on the signal conditioner board. This allows signal
conditioner boards and ranges to be changed in the field with no need for
recalibration. Cold junction compensation automatically
corrects for temperature variations at the thermocouple reference junction at the
transmitter.
Open sensor indication is standard and may be set up to indicate either upscale or
downscale. RTD excitation is provided by the transmitter. RTD connections can be of the 2-, 3-
or 4-wire type. For 3- and 4-wire connections, the transmitter automatically compensates for
lead resistance of the sensor.
With the optional dual solid state relay output
option, which has a typical response
time of only 17 ms, Laureate temperature meters
and transmitters can
serve as extremely fast and accurate ON/OFF controllers
for closed-loop temperature control.
They can also serve as
supervisory process monitors and provide alarms or shutoffs when processes exceed normal
limits. 
